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Fujita scale

Fujita scale or F-Scale, standard scale for rating the severity of tornadoes as a measure of the damage they cause, devised in 1951 by the Japanese-American meteorologist Tetsuya (Ted) Fujita (1920-98). It classifies tornadoes on a hierarchy beginning with category F0, or "light" (winds of 40-72 mph; some damage to chimneys, TV antennas, roof shingles, trees, signs, and windows), which accounts for about 28% of all tornadoes. Category F1, or "moderate" (winds of 73-112 mph; automobiles overturned, carports destroyed, and trees uprooted), accounts for about 39% of all tornadoes. Category F2, or "significant" (winds of 113-157 mph; roofs blown off homes, sheds and outbuildings demolished, and mobile homes overturned), accounts for about 24% of all tornadoes. Category F3, or "severe" (winds of 158-206 mph; exterior walls and roofs blown off homes, metal buildings collapsed or severely damaged, and forests and farmland flattened), accounts for about 6% of all tornadoes. Category F4, or "devastating" (winds of 207-260 mph; few walls, if any, left standing in well-built homes and large steel and concrete missiles thrown great distances) accounts for about 2% of all tornadoes. Category F5, or "incredible" (winds of 261-318 mph; homes leveled or carried great distances and schools, motels, and other larger structures have considerable damage with exterior walls and roofs gone), accounts for less than 1% of all tornadoes.

In 2007 the National Weather Service adopted the Enhanced Fujita scale or EF-Scale, developed by the Texas Tech Univ. Wind Science and Engineering Research Center in conjunction with other wind engineers and meteorologists. Incorporating improved knowledge of wind speeds and the resulting damage, as well as including more damage indicators (and thus allowing for a more accurate assessment of a tornado based on the destruction it caused), the scale retained the categories used by the Fujita scale but revised the associated wind speeds. Category EF0 has estimated winds of 65-85 mph; EF1, 86-110 mph; EF2, 111-135 mph; EF3, 136-165 mph; EF4, 166-200 mph; and EF5, over 200 mph.